Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net (loss) income	$ (372,503)	$ (274,285)	$ 387,011
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation	381,760	493,162	456,483
Loss on impairment of assets	678,145	860,441	109,462
Loss (gain) on disposition of assets	3,795	(2,290)	(5,382)
Loss on sale of marketable securities, net	12,146
Loss (gain) on foreign currency forward exchange contracts		8,364	(3,275)
Deferred tax provision	(106,263)	(242,034)	1,532
Stock-based compensation expense	4,880	4,856	3,507
Deferred income, net	(29,108)	(45,383)	60,061
Deferred expenses, net	(20,155)	(26,405)	(82,814)
Other assets, noncurrent	(4,914)	2,483	2,881
Other liabilities, noncurrent	(31)	(3,890)	(3,979)
(Payments of) proceeds from settlement of foreign currency forward exchange contracts designated as accounting hedges		(8,364)	3,275
Bank deposits denominated in nonconvertible currencies	3,475	1,069	5,520
Other	2,216	(211)	3,118
Changes in operating assets and liabilities:
Accounts receivable	159,098	58,872	5,269
Prepaid expenses and other current assets	6,187	19,195	(2,791)
Accounts payable and accrued liabilities	(71,085)	(180,872)	27,463
Taxes payable	(1,089)	71,719	25,490
Net cash provided by operating activities	646,554	736,427	992,831
Investing activities:
Capital expenditures (including rig construction)	(652,673)	(830,655)	(2,032,764)
Proceeds from disposition of assets, net of disposal costs	221,722	13,049	18,318
Proceeds from sale and maturities of marketable securities	4,614	51	8,000,057
Purchases of marketable securities			(6,265,846)
Net cash used in investing activities	(426,337)	(817,555)	(280,235)
Financing activities:
Repayment of long-term debt		(250,000)	(250,000)
(Repayment of) proceeds from short-term borrowings, net	(182,389)	286,589
Debt issuance costs and arrangement fees	(215)	(624)	(2,249)
Payment of dividends and anti-dilution payments	(408)	(69,432)	(486,240)
Purchase of treasury stock			(87,756)
Other			261
Net cash used in financing activities	(183,012)	(33,467)	(825,984)
Net change in cash and cash equivalents	37,205	(114,595)	(113,388)
Cash and cash equivalents, beginning of year	119,028	233,623	347,011
Cash and cash equivalents, end of year	$ 156,233	$ 119,028	$ 233,623